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319 Grant - Building the Bioretention and Raingarden Cells

- Bioretention area BEFORE the improvements. -

- Bioretention area BEFORE the improvements. -

Bioretention systems are stormwater best management practices (BMP’s) that use filtration to treat stormwater runoff. Bioretention systems are modeled after the biological and physical characteristics of an upland terrestrial forest or meadow ecosystem. These systems use vegetation, such as trees, shrubs, and grasses, to remove pollutants from stormwater runoff. Sources of runoff are diverted into
bioretention systems directly as overland flow or through a stormwater drainage system. Alternatively, a bioretention system can be constructed directly in a drainage channel or swale.

- Bioretention area AFTER the improvements. -

How Bioretention Systems Works - The first flush (initial runoff event at start of storm) stormwater runoff filters through the vegetation and soil within the bioretention area. This filtered runoff is either collected in an underdrain system or is allowed to infiltrate into the ground. Stormwater runoff after the first flush bypasses the bioretention system, as in a sand filter. Bioretention systems, like sand filters, can be used in new developments or to retrofit existing development.

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319 Grant Video - Building the Bioretention and Raingarden Cells

Grant Video - Building the Bioretention and Raingarden Cells

- Watch our video about this three year project to improve

stormwater at the Grissum Building and Power Plant site.-

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- Bioretention area AFTER the improvements. -

Advantages of Bioretention Systems - Bioretention systems have several advantages over sand filters. They provide a variety of pollutant removal mechanisms, including:
Filtration, adsorption to soil particles, and biological updake by plants, typically provide a higher degree of treatment due to the multiple removal mechanisms. Bioretention Systems - are more aesthetically pleasing than sand filters, can be readily incorporated into green spaces, streetscapes, median strips, and parking islands and provide stormwater peak flow and volume control as well as water quality control where stormwater infiltration is used, and are efficient and cost-effective.

The general design idea behind bioretention systems is to have a gentle slope for overland flow and adequate water storage. However, no water should be allowed to pond in the bioretention system for a period greater than 4 days. The ponded area should have a maximum depth of 6 inches and the planting soil should have a minimum depth of 4 feet.

No special maintenance of bioretention systems is required. Only routine periodic maintenance typical of any landscaped area (mulching, plant replacement, pruning, weeding) is needed.